package j1 import ( "bytes" "encoding/binary" "fmt" "io/ioutil" "time" ) // J1 Forth processor VM type J1 struct { dsp uint16 // 5 bit data stack pointer st0 uint16 // top of data stack pc uint16 // 13 bit rsp uint16 // 5 bit retrun stack pointer dstack [0x20]uint16 // data stack rstack [0x20]uint16 // deturn stack memory [0x8000]uint16 // memory } // Reset VM func (vm *J1) Reset() { vm.dsp = 0 vm.st0 = 0 vm.pc = 0 vm.rsp = 0 } func (vm *J1) String() string { var rstack [32]uint16 for i, v := range vm.rstack { rstack[i] = v << 1 } return fmt.Sprintf("PC=%0.4X ST=%0.4X D=%0.4X R=%0.4X", vm.pc<<1, vm.st0, vm.dstack[1:vm.dsp+1], rstack[1:vm.rsp+1]) } // LoadBytes into memory func (vm *J1) LoadBytes(data []byte) error { size := len(data) >> 1 if size > len(vm.memory) { return fmt.Errorf("too big") } return binary.Read(bytes.NewReader(data), binary.BigEndian, vm.memory[:size]) } // LoadFile into memory func (vm *J1) LoadFile(fname string) error { data, err := ioutil.ReadFile(fname) if err != nil { return err } return vm.LoadBytes(data) } // Eval evaluates content of memory func (vm *J1) Eval() { ticker := time.NewTicker(time.Second) defer ticker.Stop() for range ticker.C { ins := Decode(vm.memory[vm.pc]) if ins == Jump(0) { break } vm.eval(ins) fmt.Printf("%-30s%s\n", ins, vm) } } func (vm *J1) eval(ins Instruction) { dsp := vm.dsp pc := vm.pc + 1 st0 := vm.st0 rsp := vm.rsp switch v := ins.(type) { case Lit: st0 = uint16(v) dsp = vm.dsp + 1 vm.dstack[dsp] = vm.st0 case Jump: st0 = vm.st0 // T pc = uint16(v) case Call: st0 = vm.st0 // T rsp = vm.rsp + 1 vm.rstack[rsp] = pc pc = uint16(v) case Cond: st0 = vm.dstack[vm.dsp] // N dsp = vm.dsp - 1 if vm.st0 == 0 { pc = uint16(v) } case ALU: st0 = vm.newST0(v) if v.RtoPC { pc = vm.rstack[vm.rsp] } if v.NtoAtT { vm.memory[vm.st0] = vm.dstack[vm.dsp] } dsp = uint16(int8(vm.dsp) + v.Ddir) rsp = uint16(int8(vm.rsp) + v.Rdir) if v.TtoR { vm.rstack[rsp] = vm.st0 } if v.TtoN { vm.dstack[dsp] = vm.st0 } } vm.dsp = dsp vm.pc = pc vm.st0 = st0 vm.rsp = rsp } func (vm *J1) newST0(v ALU) uint16 { T, N, R := vm.st0, vm.dstack[vm.dsp], vm.rstack[vm.rsp] switch v.Opcode { case 0: // T return T case 1: // N return N case 2: // T+N return T + N case 3: // T&N return T & N case 4: // T|N return T | N case 5: // T^N return T ^ N case 6: // ~T return ^T case 7: // N==T if N == T { return 1 } return 0 case 8: // N>T return N >> (T & 0xf) case 10: // T-1 return T - 1 case 11: // R (rT) return R case 12: // [T] return vm.memory[T] case 13: // N<